We plan to study clinical applications of a new viewer for tomographic scans which will allow the physician to examine multiple scan sections simultaneously in their proper relationship in all three dimensions. Test images already produced on a prototype device clearly show stereopsis and parallax depth cues characteristic of a real three dimensional object. Our experience viewing head scans on the device has shown that certain anatomical and pathological features important in cancer detection are more readily appreciated on the 3-D viewer than on conventional planar imaging facilities such as a T.V. viewer or film. The device will be interfaced to an X-ray treatment planning system which will allow three dimensional dose calculations. The dose distribution in three dimensions will be superimposed over the diagnostic image which is also displayed in three dimensions. The resulting display will allow immediate visualization of patient doses out of the central plane prompting the radiotherapists to work in "volume distributions", rather than "planar distributions." This should improve visualization of the X-ray dose distribution, resulting in more effective therapy. We will investigate the extent to which this improved visualization results in improved therapy management. We will evaluate this device using X-ray CT and B-scan ultrasound images, also treatment dose profiles, to determine the extent to which these data are more comprehensible when viewed in 3-D.